EXPLORE THE BAY

Imagine a trail that has no beginning or end, does not follow a path, and can take you to world-class destinations. This is the San Francisco Bay Area Water Trail – a network of access sites along the shoreline that allow non-motorized small boats to explore all San Francisco Bay has to offer. You choose your route and your boat type from each Water Trail “trailhead” – and from there you can discover jaw-dropping views, amazing wildlife, and rich history – San Francisco Bay like you’ve never seen it before. The pages in this section will introduce you to the Water Trail, provide tips on how to boat among wildlife, and give you a sample of the boats and experiences you may find during your explorations.

About the Water Trail

A Unique Trail

The San Francisco Bay Area Water Trail is a growing network of boat launching and landing sites, or “trailheads,” around the San Francisco Bay. The Water Trail’s network of sites encourages awareness of facilities, programs, rental concessions, and other information to help non-motorized small boaters and boardsailors have safe enjoyable days on the Bay.

The Water Trail is unique among the trails found in the Bay Area. It is not a linear trail, but a network of launching and landing sites that can take you to iconic and incredible destinations on the San Francisco Bay and its major tributaries – the San Joaquin River, the Napa River, and the Petaluma River.

Some locations offer nature and solitude with opportunities to see a huge variety of birds and wildlife, others offer dynamic urban waterfronts with incredible sights and views. Each trailhead enables non-motorized small boat users to enjoy the historic, scenic, cultural, and environmental richness of San Francisco Bay and its nearby tributary waters. With over 500-square miles of navigable waters, the San Francisco Bay and its tributaries are the Bay Area’s largest open space. The possibilities are limitless.

The Water Trail program continues to grow with the support and input from the boating community and an advisory committee representing a broad range of interests and expertise. We invite you to safely explore the different types of experiences that can be found on the Bay.

Water Trail Program Goals

Create a coordinated set of access locations allowing for single point, multiple point, and multi-day excursions

Program History and Management

The vision of the Water Trail Program began with Bay Access, a non-profit group working to ensure future access for non-motorized small boat users on the Bay, and planning support from the National Park Service. This vision became law in 2005 with the passage of the Water Trail Act by the California Legislature (Hancock, AB 1296).

Today, this regional, nine-county program is being implemented under the leadership of the State Coastal Conservancy (Conservancy) in close collaboration with the Association of Bay Area Governments / Metropolitan Transportation Commission (ABAG/MTC), the San Francisco Bay Conservation and Development Commission (BCDC), and State Parks Division of Boating and Waterways (Cal Boating), plus an advisory committee representing a broad range of interests and expertise.

Types of Boats

Many Ways to get on the Water

There are many different ways to get out on the Bay. We invite you to learn about the most common human-powered boats and boards.

Canoe

Canoes are open-hulledboats about 12 to 19-feet long. Paddlers use single-blade paddles and face the direction of travel. A canoe is better suited for protected waters such as sloughs and creeks than the open Bay.

Dragon boat

The roots of dragon boat racing go back over 2,000 years to the southern provinces of China. The modern dragon boat is open-hulled and 40-feet long, and holds 20 paddlers (sitting side by side facing the bow or the direction of travel), a drummer who sets the cadence, and a person who controls the direction of the boat. Dragon boats are involved in many races and festivals, and some designs are stable enough for the open waters of the Bay.

Kayak

Kayaks are small, relatively narrow, close hulled, and use a double-bladed paddle. There are many different styles of kayaks, with the sea kayak being a popular type found on the Bay. Kayaks are well suited for touring and many have space for equipment for overnight excursions.

Kayaking, San Francisco Waterfront

Kiteboarding

Kiteboarding or kitesurfing is an adventurous sport where an individual is attached to a large maneuverable kite via a harness that propels the rider and a board across the water. Fans of this sport consider the Bay Area a world-class destination for kiteboarding. Baywinds Park and Crissy Field are good locations to see this sport in action.

Kiteboarders, Baywinds Park

Outrigger canoe

The outrigger canoe is closely tied to Polynesian culture, where it is believed that the outrigger canoe was developed. There are many variations of outrigger canoes types, but an open-hulled one that seats six paddlers is popular. The outrigger canoe is very stable because of the outrigger, is well suited to the Bay’s open waters, and is popular for racing.

Outrigger Canoers, photo provided by Jennifer Villamin

Rowboat/Dinghy

A rowboat is a wide, heavy boat that is usually rowed by one person. It is well suited to touring since it is stable and there is space for equipment. It is often used to get to shore from a larger boat moored offshore.

Rowing

The shells used in rowing are very narrow and long and generally hold one, two, four, or eight rowers. The oars are held in place, usually with an oarlock. There are two types of rowing: sweeping where every rower has one oar; and sculling where every rower has two oars. Rowers face the back (stern) of the boat and there is often a coxswain who helps steer and guide the boat. Rowing is generally done in calmer waters.

Stand up paddleboard

Stand up paddleboarding (SUP’ing) has its origin in the Hawaiian Islands. It consists of a board and paddle and is a fast growing sport. SUP’ing is versatile and suitable for touring, racing, and surfing and a wide range of athletic types. Several outfitters in the Bay Area offer SUP yoga and pilates lessons.

Surf Ski

A surf ski is a long, narrow, lightweight kayak with an open (sit-on-top) cockpit, usually with a foot pedal-controlled rudder. A surf ski (with an experienced paddler) is a very effective craft for paddling in big surf. Its narrowness and length helps it cut or punch through large broken waves. Surf skis are extremely fast and are often used in competitions.

Whaleboat

Whaleboats, or “Monomoys” were used in life-saving rescues and whaling for most of the 20th century. These open-water boats weigh about one ton and carry a crew of ten: eight rowers, a coxswain, and a bowhook. Team racing and touring is popular, and whaleboats are very stable.

Windsurfing

Windsurfing combines elements of surfing and sailing. There is a long board, usually six – ten feet long, powered by wind on a sail. Bay conditions are well suited to windsurfing and many fans consider the Bay Area the best place on the West Coast for boardsailing.

Types of Experiences

Kayaks, McNear’s Beach

Make the Bay Your Playground

Many of us have walked, jogged, or biked along the Bay, enjoying our shoreline for exercise, relaxation, wildlife watching, or for personal reflection. The Bay offers a completely different type of experience – out on its waters. This great 450-square mile estuary has many opportunities for recreation for those that venture out beyond land. Some are thrill seeking, and others are quiet and peaceful. We invite you to explore, discover, learn, and enjoy!

The following are a sample of the diverse experiences our Bay has to offer. Visit our map page for information on specific sites.

Urban

Paddle, canoe, or row along the San Francisco waterfront, taking in views of bridges and the skyline while witnessing the hustle and bustle of city life from the water. Or head over to the Oakland Estuary and discover the mix of swanky condos, restaurants, and warehouses found along the waterfront.

Quiet/Wildlife

We share the Bay with an amazing diversity of wildlife – seasonal visitors and year-round neighbors. Every time you get out and explore you will be surprised and delighted. Enjoy a meandering slough, lunch on a secluded beach, or soak in views of marshes and wetlands teeming with wildlife – you will forget you are in a major metropolitan area.

Kayakers, Petaluma River

Islands, Rivers, and Sloughs

Not only do we have miles of open Bay to explore, but the Water Trail also includes rivers, islands, and sloughs. Explore tidally influenced rivers such as the Napa and Petaluma Rivers, both of which offer miles of play with many attractions to entice you along the way. For the more experienced, head over to Angel Island and find yourself in the jewel of the Bay.

Stand up paddler, by 101surfsports.com

Adventure

The winds, tides, and currents found on the open Bay offer many challenging conditions thrill-seekers thrive in. Boardsailors (windsurfers and kitesurfers) have access to world-class windy conditions with scenery that is unsurpassed. Advanced paddlers have miles of exploration to fine tune paddling skills and enough challenging wind and wave conditions to get an adrenaline rush.

Ferry Building, by Wilfred J. Jones

Attractions

The Bay has no shortage of attractions for both locals and tourists. Soak up local flavor at many restaurants located on the shore. View beautiful bridges from many locations around the Bay. Catch a “splash hit” from a Giant’s baseball game at McCovey Cove (AT&T Park). Enjoy views of houseboats and Mt. Tamalpais in Sausalito. Visit the historic vessels at San Francisco Maritime National Historical Park. You will not run out of things to discover.

Nature Viewing

Pacific Harbor Seals, by Mark Rauzon

Observe From a Distance

San Francisco Bay is the largest estuary west of the Mississippi and is a complex and rich ecosystem surrounded by over seven million people. The Bay supports more than 500 species of wildlife, including 105 threatened and 23 endangered species, such as the California clapper rail and salt marsh harvest mouse.

The opportunities to see wildlife, enjoy the water, and travel to areas inaccessible from land, are some of the reasons we enjoy getting out on the Water Trail. We need to remember that we can often cause a disturbance to the critters we are trying to see. There are ways to lessen our impact and in return, be rewarded with seeing wildlife behave naturally, as well as knowing that we are protecting our resources.

Pay attention to behavior signs from wildlife that you are too close.

Disturbance signs usually begin with an alert response, where an animal stops its activity such as sleeping, foraging, or resting, and begins to watch you. If the animal gets more threatened this usually escalates to flushing behavior (the animal moves away from the disturbance suddenly). Put yourself in their “shoes”!

Maintain the recommended buffer distances from sensitive species.

Remember that there is variability amongst individuals and areas. Even if you are far away, if the animal shows a disturbance response, you are too close. It can be very rewarding to learn the natural behavior of different species. The use of binoculars is an excellent method of observing wildlife without causing a disturbance.

Canada Goose family, Horseshoe Cove

Paddle at a constant heading and speed when passing wildlife.

When passing by wildlife, maintain constant heading and speed, avoid sudden stops or sudden changes in heading or speed, and avoid paddling directly at animals.

Plan your trip to avoid sensitive habitat.

Avoid areas where you know there are sensitive species, such as harbor seal haul-outs, narrow channels, high tide refuge, roosting sites, and nesting colonies. Do not attempt to rescue injured animals. Instead contact your local wild animal rescue group or Marine Mammal Center.

Prevent the spread of invasive species.

San Francisco Bay is at risk of weed invasions that may colonize new areas in the Bay. Weeds may be dispersed by mud or sand attaching to gear or boating equipment. Help protect the Bay and your gear by rinsing off your equipment and boat before you leave or visit another site.

Protect sensitive habitat.

Only launch and land in designated areas and avoid making unauthorized landings or informal trails. Trampling not only destroys habitat for endangered species by destroying vegetation or spreading invasive species, but boaters could inadvertently harm endangered species by disturbing nests or stepping on small animals such as the salt marsh harvest mouse while landing or entering habitat.

Planning Documents

Extensive research, coordination, and outreach have occurred to develop a system and plan for implementation of the Water Trail. The process of designation builds several key documents that have been developed with input and oversight from a wide variety of experts and stakeholders. Key documents that have been developed for the Water Trail are briefly described below.

Enhanced San Francisco Bay Area Water Trail Plan (December 2011). A guide to trail implementation for the agencies and organizations that will develop and manage Water Trail access points and programs. Recommended policies and procedures in the Plan define how the Water Trail will take shape over time by guiding trail planning, development, and management on organizational, programmatic, and trailhead project-specific levels.

San Francisco Bay Area Water Trail EIR (December 2011). Programmatic CEQA analysis for implementation of the Water Trail Program. Includes discussion of potential impacts, thresholds, and mitigation measures developed in coordination with resource agencies and responses to comments.

Water Trail Education and Outreach Program (November 2011). Blueprint for education, outreach, and stewardship activities presented in three broad themes: promote personal and navigational safety; create a comprehensive education program to increase environmental education and interpretation, and to support access to the Water Trail for all interested users; and, develop a Water Trail Ethic emphasizing safe, low-impact boating practices and stewardship of the Bay.

San Francisco Bay Area Water Trail Accessibility Plan (January 2015). Provides region-specific guidance focused on improving the accessibility of launching and landing sites for persons with disabilities using non-motorized small boats. It provides guidance for both site owners and for the Water Trail implementation and designation process.

Habitat Restoration

The San Francisco Bay is one of America’s great estuaries. Over the years, urbanization and the transformation of open spaces to more intensive land uses have contributed to the marginalization of the region’s native species and their habitats — wetlands in particular.

Scientists agree that the Bay needs at least 100,000 acres of healthy wetland habitat to function effectively. There are approximately 51,300 acres of tidal marsh in the Bay as of 2015. More than 24,000 additional acres of Bay wetlands are planned and permitted for restoration. In addition to habitat, restored wetlands provide exciting areas for recreation and wildlife viewing.

In 2016, Bay Area residents overwhelmingly voted for the San Francisco Bay Clean Water, Pollution Prevention and Habitat Restoration Measure, which will raise approximately $25 million annually over twenty years to fund shoreline projects that will restore thousands of acres of wetland habitat, enhance recreational access to the Bay, improve water quality, and protect vulnerable infrastructure.

The Water Trail’s mission complements the wildlife-oriented public access and recreation goals associated with the restoration projects.

Weed management volunteer group at Pond A17 on the Don Edwards San Francisco Bay National Wildlife Refuge, which is managed by the USFWS. The restoration of Pond A17 was planned by the South Bay Salt Ponds Restoration Project, led by the California Coastal Conservancy. – Photo provided by the San Francisco Bay Bird Observatory.

Additional Information

Bay Wildlife

The San Francisco Bay is the largest estuary in western North America, encompassing the San Francisco Bay and the Delta of the Sacramento and San Joaquin rivers. The Estuary’s watershed extends from the ridgeline of the Sierra Nevada mountains to the Golden Gate, including almost 60,000 square miles and nearly 40% of California. It is all one system, however, connected by freshwater outflow to the pacific and by the ebb and flow of ocean tides far upstream into the Delta.

The Estuary’s waters and wetlands are a biological resource of tremendous importance – providing critical winter feeding habitat for over a million migratory birds, a productive nursery for many species of juvenile fish and shellfish, and a year-round home for a vast diversity of plants and animals.

Paddling the Water Trail offers a unique and incredible opportunity to view and learn about the wildlife that lives in and around the Bay. Remember to be considerate of the wildlife you do encounter and avoid disturbing them by maintaining buffer distances. They need their energy for feeding, raising young, and survival.

Birds

The San Francisco Bay has been recognized as a Western Hemisphere Shorebird Reserve Network site of international importance due to the habitat it provides for resident and migratory birds. San Francisco Bay provides the most important complex of wetland habitat for migratory and wintering waterbirds on the Pacific Coast, including wintering habitat for more than 50% of the diving ducks on the Pacific Flyway and more than 500,000 individuals annually.

Early accounts of the San Francisco Bay Area frequently mention the abundance of birds, but the population has decreased due to a combination of many stressors such as habitat loss, pollution, and invasive species. This habitat loss happens in both the summer and wintering areas, resulting in more adverse impacts. Although there are variations, many bird species are sensitive to human disturbance, including disturbance by non-motorized small boats – remember to be considerate of the wildlife you do encounter and avoid disturbing them by maintaining recommended buffer distances.

Male Surf Scoter, by Tom Grey

Pacific Flyway

Many waterfowl use San Francisco Bay in winter months for flocking, feeding, and forming pair bonds in preparation for spring migration to their breeding grounds in Alaska, Canada, and the northern United States. The peak season is November through mid-March, but this can vary year to year. By the time birds stop to rest, their fat reserves are nearly exhausted and San Francisco Bay provides food for them to refuel and continue migration.

Threatened and Endangered Species

Ridgway’s Rail

Ridgway’s Rail, by Tom Grey

The Ridgway’s rail (Rallus longirostris obsoletus) is a large, hen-like bird with a long, slightly down-curved bill that is restricted to the marshes around San Francisco Bay. Once abundant, it is currently a federal endangered species and California state fully protected species and is very sensitive to disturbance. Thousands of Ridgway’s rails were eliminated by market hunters from the gold rush until passage of the Migratory Bird Treaty Act. Since then, the loss of over 85% of marsh habitat in the Bay has reduced population numbers.

Populations of Ridgway’s rails are found in remnant salt marshes such as Bair and Greco Islands, along Coyote Creek, and within the Don Edwards San Francisco Bay National Wildlife Refuge. Smaller populations can be found in western Contra Costa, eastern Marin, and northern Alameda Counties; northern San Pablo Bay; along the Petaluma River; and along major creeks and marshes in Sonoma and Napa Counties.

Ridgway’s rails inhabit a range of salt and brackish water marshes. They use the network of small tidal sloughs for foraging and quick escape. The Ridgway’s rail breeding season usually begins in February and can last as long as August. Both male and female share in incubation and chick rearing. Their nests are often found immediately adjacent to a channel, many of which are navigable by shallow-draft non-motorized small boats, making nest sites particularly vulnerable to disturbance. Human disturbance into Ridgway’s rail habitat would likely disturb incubating or brooding birds, potentially reducing reproductive success by breeding pairs (possibly to the point of abandonment of nests, eggs, or young) and possibly destroying active nests. A lost nesting effort, even by a single pair, may have population-level implications for this critically-endangered species.

During very high winter tides, Ridgway’s rails are often concentrated in limited high-tide areas, referred to as “refugia.” Marshes used to have vegetation zones with low, middle, and high marshlands. The high marsh zones act as refuge for many salt marsh animals escaping high tides. These refuge areas have been largely destroyed, resulting in small patches with high concentrations of animals. During high tide events, rail species are particularly vulnerable to predation by mammals and raptors, or other larger birds. If non-motorized small boat users approach high-tide refugia during such extreme tides, they may flush rails into areas where the likelihood of predation would increase. During extremely high winter tides, when much of the marsh plain is inundated, determining the locations of channels, or marsh edge, may be difficult. Boaters should remain at least 50 feet from the edge of the marsh, as demarcated by emergent or inundated vegetation, or other features that may be visible, and not approach vegetation that is not inundated during those times. This means non-motorized small boat users should avoid channels less than 100 feet wide where rails may be present.

Sources/Further Reading

Western snowy plover

Western Snowy Plover, by Tom Grey

The Pacific Coast western snowy plover (Charadrius nivosus nivosus) is a small, threatened shorebird that forages for small invertebrates. Its population has declined due to poor reproductive success, which is likely due to habitat loss and alteration, human disturbance, and predation.

Although snowy plovers often nest on beaches, they also nest on salt ponds and levees in the South Bay. Nesting season is typically March through September. Plover nests are camouflaged and are barely visible to even the well-trained eye. Plovers are polyandrous (the female may breed with more than one male), and the female typically deserts the brood shortly after hatching, leaving the chick-rearing duties to the male.

Human activities and predation are key factors in the decline of breeding sites and populations. Western snowy plovers can be disturbed if boaters disembark near salt ponds or levees – either flushing the adults or stepping on the eggs. If the adult leaves the nest, predation by California gulls, common ravens, northern harriers, or red-tailed hawks may occur. To help protect snowy plovers, please keep a distance of 656 feet (200 meters) from plovers and do not land near salt ponds and levees.

Sources/Further Reading

Protecting Birds

For many wintering waterfowl, the amount of energy reserves built up during the winter months directly impacts migration, survival, and reproductive success. Although there are variations, many waterfowl are sensitive to human disturbance, including disturbance by non-motorized small boats.

Disturbance includes human activity that is an intrusion or interruption in the natural, daily activity of an animal. Usually there is an alert response first, such as the bird stops its normal activity and watches you. This usually escalates to “flushing” in which a bird or group of birds moves away from or flees an approaching threat. In waterbirds this looks like swimming, diving, or flying. Because birds concentrate their activities where there is the best opportunity to maximize energy gain, flushing may reduce the time waterbirds spend feeding or resting and may cause them to be displaced to less than optimal feeding and resting areas, or even abandon foraging habitat. Repeated flushing costs energy, and may have cumulative effects on migratory energy and reproductive success or in a local decline in abundance. Numerous small disturbances may be more damaging than fewer, larger disturbances because birds may not have time to recover between disturbances.

To help waterfowl, maintain a buffer distance of 250 meters, or approximately 800 feet, from congregations of waterbirds to minimize disturbance. If this buffer distance is not possible, users should move steadily through, parallel to, or away from birds.

Sources/Further Reading

Mammals

Pacific harbor seal

Pacific harbor seals (Phoca vitulina) are the only marine mammal resident in San Francisco Bay year-round. (The California sea lion uses the Bay seasonally for foraging, and some individuals use the floating docks at Pier 39 as a haul-out site). Harbor seals have spotted fur that varies in color. Males and females are about the same size, reaching a maximum of 300 pounds (140 kg). Harbor seals pup March – May and molt June – July. A pup can swim at birth and will sometimes ride on its mother’s back when tired. Adult females usually mate and give birth every year. They may live 25 to 30 years.

Harbor seals tend to congregate on the same terrestrial sites, called “haul-out sites” year after year. Their numbers are highest during the pupping (March – May) and molting (June-July) seasons. Haul-out sites are usually located where there is ease of access to water, proximity to food, and minimal disturbance. Some haul-outs are used year-round, while some are used seasonally. Some sites may be particularly important to seals during pupping and molting as these areas provide shelter from storms. Studies show disturbance by humans has been shown to cause declines in numbers of seals using sites and if sufficiently disruptive, disturbance may cause seals to abandon traditional haul-out sites, and may affect reproductive activities during pupping season.

Disturbance to haul-out sites is often cited as one potential reason for the lack of overall population increase in San Francisco Bay, in contrast with increases seen on the outer coast. Disturbances from kayaks and canoes are comparable to or even greater than those observed for powered vessels. Motorboats tend to maintain constant speed and heading, whereas paddle boats tend to move closer to the shore, approach directly, and change speed and direction frequently. The image of a boat that is slow, quiet, and low to the water may appear more like a predator than other watercraft.

Harbor seals are federally protected under the Marine Mammal Protection Act. The Marine Mammal Protection Act prohibits take, which is harassing, hunting, etc. of a marine mammal. Harassment is any act of pursuit, torment, or annoyance which has potential to injure a marine mammal in the wild, or potential to disturb by causing disruption of behavioral patterns, including migration, breathing, nursing, breeding, feeding or sheltering.

The following guidelines will help you protect Pacific harbor seals from disturbance:

Maintain minimum distance of 328 feet (100 meters) from haul-out at all times and at least 492 feet (150 meters) from March – July.

Sources/Further Reading

California sea lion

California sea lions (Zalophus californianus) use San Francisco Bay for foraging, but breed elsewhere (unlike Pacific harbor seals which breed in the Bay). These noisy, intelligent creatures are members of the “walking” seal family whose members have external ear flaps and large flippers that they use to “walk” on land. Males reach 850 pounds and seven feet in length, and females grow to 220 pounds and six feet in length.

In San Francisco Bay, the greatest numbers of California sea lions are found during the winter herring run (December – February). They are opportunistic feeders and will prey mostly on schooling species, but also leopard sharks, shrimp, and crabs. The floating docks at Pier 39 are one of the few known terrestrial locations where sea lions are observed congregating in the Bay.

In the event that you do see an injured marine mammal:

Do not touch, pick up, or feed the animal

Observe the animal from a distance and keep people and dogs away

Note physical characteristics such as size, presence of external ears, and fur color

Salt marsh harvest mouse

The salt marsh harvest mouse (Reithrodontomys raviventris), is a tiny, endangered mouse that is endemic to San Francisco Bay, meaning it is found nowhere else in the world. Within San Francisco Bay there are two subspecies – a North Bay and a South Bay subspecies. Its scientific name means it is a grooved-tooth mouse with a red belly. The mouse is very small, weighing only 9-14 grams and is approximately three inches in length. Not much is known about the ecology of the mouse as it is secretive and difficult to study.

Unfortunately, the salt marsh harvest mouse has been listed as an endangered species since 1970. The primary threat to the mouse’s survival is habitat loss. Since it is only found around San Francisco Bay, the loss of our marshes has caused a decline in mice numbers. Boaters should not land their craft in marshes to prevent trampling and inadvertently stepping on a mouse or its nest.

Sources/Further Reading

Fish

The Estuary’s waters and wetlands are a biological resource of tremendous importance — providing a productive nursery and hunting ground for many species of fish.

Bat Ray

Bat Ray, by flickr user HeyJupiter

Bat rays (Myliobatus californica) are found in sandy and muddy bays and sloughs, as well as rocky areas. They swim gracefully by flapping their batlike wings, or pectoral fins. The flapping motion, when done in the sand, exposes buried invertebrates that they feed on. They also use their snout to dig for prey and have fused teeth that can crush strong shells, which they then spit out, eating the soft, fleshy parts. Bat rays can be found feeding in the intertidal zone during high tide.

Bat rays mate during the summer months, followed by a gestation period of nine to 12 months. They give birth to two to ten live young. Pups emerge tail first and their stinging spines are covered with a sheath that sloughs off to protect the mother during birth. They can grow to a wingspan of six feet, but this size is uncommon.

Although they have one to three venomous barbed spines at the base of their tail, the docile animals only sting to defend themselves.

For many years, oyster growers trapped bat rays because they thought bat rays ate large numbers of oysters. But recently researchers have discovered that bat rays rarely eat oysters, and that crabs were destroying the oyster beds. The oyster growers were actually causing the destruction of their own oyster beds by trapping bat rays, which eat crabs.

Northern anchovy

Northern Anchovy, by Beth Hoffman

Northern anchovy (Engraulis mordax) is the most abundant fish in San Francisco Bay. This small fish that is only 7 – 9 inches makes up the largest biomass in San Francisco Bay. It is an important food source for larger predators such as California brown pelicans, terns, sharks, seals, Chinook and coho salmon, and other many other fish species. In San Francisco Bay northern anchovies occur from Suisun Bay to South Bay. There is a seasonal influx of the northern anchovy in the spring when water temperatures and plankton production rises in the bay. Adults exit in the fall, although some late-spawned juveniles overwinter within the Bay.

Caspian Tern Feeding Northern Anchovy to Chicks, by David P. Craig

Northern anchovy spawn throughout the year. Females can produce up to 130,000 eggs per year. Depending on the temperature, it takes two to four days for the eggs to hatch. Larvae growth is fast in the warm bay environment. These species are short-lived; most live less than four years. The bay provides good habitat for reproduction because of the ample food for adults and larvae.

Topsmelt

Topsmelt, by Ken-ichi

Topsmelt (Atherinops affinis) are a small fish that many recreational anglers catch and find tasty. There are five subspecies, with only one subspecies (A. affinis affins) found in San Francisco Bay. They can be observed spawning in the Bay and small schools of larvae can often be found near the surface of the water, particularly in tidal basins or sluggish waters. Juveniles are generally found in the open bay or coastal kelp beds. Topsmelt are an important prey item for many birds and fishes and are fished both commercially and by recreational sports fisherman.

Adult topsmelt move into shallow sloughs and mud flats in the spring and summer to spawn, with peaks in May and June. Eggs become entangled in aquatic vegetation and often form clusters. Hatching time varies based on temperature and can range from 35 days to less than 9 days. Topsmelt mature in their second or third year and may live six to nine years.

Invertebrates

The daily turn of the tides has a profound influence on the San Francisco Bay. Much of the Bay is less than 15 feet deep, so as the tide recedes vast mudflats are exposed. These mudflats support a complex ecosystem of crabs, clams, worms and other invertebrates. When exposed at low tides, these mudflat organisms provide a rich buffet for birds and terrestrial species. Similarly, when the tide turns and these areas become submerged again, aquatic hunters like bat rays and leopard sharks move in to feed.

California horn snail

California Horn Snail, by flickr user stonebird

Although tidal mudflats appear to be bare, they actually support a large community of shellfish, snails, and other invertebrates which are extremely important for wintering waterfowl and shorebirds.

One such invertebrate that lives in the tidal mudflats is the California horn snail (Cerithidea californica), found from Central Baja to Bolinas Bay. It eats decaying plants and algae and benthic diatoms (a one-celled form of algae that lives at lower depths of the water).

Biologists are very interested in the California horn snail because it may be an indicator of the marsh community. The California horn snail is a host for parasitic worms called trematodes. These worms start their life cycle in a snail and eventually end up in birds, without causing harm to the birds. Since trematodes have a complex life cycle, it is a good indicator that predator-prey relationships are working. Biologists studying a marsh in Santa Barbara found that the more birds found at a site, the more trematodes were also found. The California horn snail hosts more than 20 trematode species, making it a species that wetland managers may be able to use for restoration decisions.

Sources/Further Reading

Experiences

Kayaks, McNear’s Beach

Make the Bay Your Playground

Many of us have walked, jogged, or biked along the Bay, enjoying our shoreline for exercise, relaxation, wildlife watching, or for personal reflection. The Bay offers a completely different type of experience – out on its waters. This great 450-square mile estuary has many opportunities for recreation for those that venture out beyond land. Some are thrill seeking, and others are quiet and peaceful. We invite you to explore, discover, learn, and enjoy!

The following are a sample of the diverse experiences our Bay has to offer. Visit our map page for information on specific sites.

Urban

Paddle, canoe, or row along the San Francisco waterfront, taking in views of bridges and the skyline while witnessing the hustle and bustle of city life from the water. Or head over to the Oakland Estuary and discover the mix of swanky condos, restaurants, and warehouses found along the waterfront.

Quiet/Wildlife

We share the Bay with an amazing diversity of wildlife – seasonal visitors and year-round neighbors. Every time you get out and explore you will be surprised and delighted. Enjoy a meandering slough, lunch on a secluded beach, or soak in views of marshes and wetlands teeming with wildlife – you will forget you are in a major metropolitan area.

Kayakers, Petaluma River

Islands, Rivers, and Sloughs

Not only do we have miles of open Bay to explore, but the Water Trail also includes rivers, islands, and sloughs. Explore tidally influenced rivers such as the Napa and Petaluma Rivers, both of which offer miles of play with many attractions to entice you along the way. For the more experienced, head over to Angel Island and find yourself in the jewel of the Bay.

Adventure

The winds, tides, and currents found on the open Bay offer many challenging conditions thrill-seekers thrive in. Boardsailors (windsurfers and kitesurfers) have access to world-class windy conditions with scenery that is unsurpassed. Advanced paddlers have miles of exploration to fine tune paddling skills and enough challenging wind and wave conditions to get an adrenaline rush.

Ferry Building, by Wilfred J. Jones

Attractions

The Bay has no shortage of attractions for both locals and tourists. Soak up local flavor at many restaurants located on the shore. View beautiful bridges from many locations around the Bay. Catch a “splash hit” from a Giant’s baseball game at McCovey Cove (AT&T Park). Enjoy views of houseboats and Mt. Tamalpais in Sausalito. Visit the historic vessels at San Francisco Maritime National Historical Park. You will not run out of things to discover.